Variation in morpho-physiological, biochemical and molecular responses of two Eucalyptus species under short-term water stress

The genus Eucalyptus occurs in a wide range of environmental conditions, including rainforests, subalpine, arid/semi-arid and moist temperate zones. It includes species with the capacity to cope with extremely low water potential. This study aims to screen water stress tolerance in two Eucalyptus species under nursery conditions. Inter-specific variation in morphological, physiological, biochemical and molecular parameters in two Eucalyptus species (E. tereticornis and E. camaldulensis) with contrasting levels of tolerance to progressive short term water-deprived condition was evaluated. Water stress reduced growth measured in terms of root:shoot ratio and specific leaf area (SLA), photosynthetic parameters, leaf water potential and relative water content (RWC) in both genotypes. Biochemical parameters including total sugars, phenol, phytohormones (indole acetic acid and abscisic acid) and proline were found to significantly increase during stress in both genotypes. Water responsive transcripts like osmotin and DREB/CBF registered significant expression variation in the two genotypes, suggesting their key role in regulating water stress tolerance in Eucalyptus.